Self-sealing metallic overwrap



Nov. 6, 1962 R. E. JACKE SELF-SEALING METALLIC OVERWRAP 2 Sheets-Sheet 1Filed Jan. '7, 1958 E M J 6 D N o M M R ATTORNEY Nov. 6, 1962 R. E.JACKE SELF-SEALING METALLIC OVERWRAP 2 Sheets-Sheet 2 Filed Jan. '7,1958 RAYMOND I /A/(E ATTORNEY ired States T ice 3,062,432 SELF-SEALINGMETALLIC OVERWRAP Raymond E. .lacke, Louisville, Ky., assignor toReynolds Metals Company, Richmond, Va., a corporation of Delaware FiledJan. 7, 1958, Ser. No. 707,490 8 Claims. (Cl. 22987) This inventionrelates generally to an improved laminated sheet having a metallicsurface and more particularly to such a sheet for use in overwraps orlners and in which the sheet may be self-sealed, in enveloping relationto the material to be enclosed, by application of heat to its metallicsurface. In addition, the invention further relates to an improvedmethod and apparatus for producing the improved sheet.

Laminated sheet of this general type which includes layers of metallicfoil, adhesive and paper is well known and has been employed in manyspecialized wrapping and lining usages. More specifically, thisinvent'on relates to providing such a sheet with apertures in themetallic foil layer so that when heat is applied to the metallic layer,the adhesive may readily flow through the apertures and spread upon themetallic layer surface thereby to provide a medium for bonding themetallic layer to itself by a self-sealing action in regions where suchlayer is in contact with itself. Difiiculty is experienced in providingapertures which enable this purpose to be accompl shed without, at thesame time, unduly weakening the sheet; unduly limiting the spread ofadhesive which, of course, would weaken the self-sealing action; orunduly interfering with rapid production of a clean sheet due to flakingof the metallic surface, accumulation of adhesive on theaperture-forming means or inability to maintain accurate depths ofapertures Over a period of time.

It is these and similar problems in the manufacture of, and inbroadening the capabilities of, laminated sheet comprising metallic,adhesive and paper layers, which my invention overcomes. For simplicityof description, such sheet will hereinafter be referred to generally asoverwrap although it will be understood that the invention comprehendsthe use of such sheet for lining of containers or in other ways in whichthe sheet envelops a material or object and wherein its self-sealingfunction is employed. As an illustrative example of one use of theinvention, an overwrap suitable for efficiently enwrapping aconventional loaf of bread will be disclosed.

An object of the invention is to provide an improved self-sealingmetallic type overwrap which contains a plurality of perforationsadapted to dIr-ect sufiicient adhesive to the metallic surface to insurea secure metallic to metallic sealing of the overwrap.

Another object is to provide an improved self-sealing metallic typeoverwrap which contains a plurality of'perforation arranged to avoid anytendencythereof to act as tear strips during normal usage of theoverwrap.

Another object is to provide an improved method for rapidly perforatingan imperforate web of laminated metallic type overwrap material.

A further object is to provide an improvedapparatus for rapidlyperforating an imperforate web of laminated metallic type overwrapmaterial under an exacting control with respect to depth of perforation.

Still a further object is to provide an improved overwrap for a loaf ofbread.

In carrying out my invention, I provide a spooling machine to which arapidly travelling imperforate Web of overwrap is supplied under tensionfurnished by that machine, and on which the web may be spooled afterbeing perforated. Cooperating with the spooljng ma.- chine i an improvedperforating means comprising a plurality of rotatable toothed bladeswhich are driven by contact with the moving web and which are adjustedby a biasing means to effect a closely controlled depth of penetrationof the web. A resilient and rotatable back ng roll is disposed on thepaper side of the travelling web and serves as a backing against whichthe pressure of the blade biasing means is expended as the blade cutsthrough the metallic side of that web. Each blade includes a number ofspaced cutting teeth on its periphery, such teeth having a configurationwhich not only minimizes the flaking or detach'ng of particles of themetallic layer from that layer, but also minimizes the tendency of theexposed adhesive to build up on the blade. Following the perforatingstep, the perforated web as an intermediate article of manufacture maybe stored for later use or may be directed immediately into packagingmach'nery in which it is cut transversely to form the improved overwrapas a separate article.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. Myinventionitself, however, both as to its organization and method ofoperat on, may be best understood by reference to the followingdescription, taken in conjunction with the accompanying drawing inwhich:

FIG. 1 is diagrammatic side elevation view showing the path of travel ofthe web under treatment;

FIG. 2 is a transverse view along line 22 of FIG. 1, showing therelation of the backing roll and perforating blades;

FIG. 3 is a view partly in section taken on line 3-3 of FIG. 2;

FIG. 4 is a plan view partly in section taken on line 44 of FIG. 2;

FIG. 5 is a side elevation view of a typical perforating blade, only aportion of the teeth being shown;

FIG. 6 is a plan view of a'finished overwrap;

FIG. 7 is a sectional view taken on line 7-7 of FIG. 6, and to a greatlyexaggeratedscale; and

FIG. 8 is a perspective view of a loaf of bread enwrapped with theoverwrap of FIG. -6.

Referring first to FIGS. 6 and 7, a typical overwrap article made inaccordance with the invention may comprise a rectangular sheet havingparallel side edges 10 and 11 and parallel end edges 12 and 13. Thesheet is of a laminated construction comprising a relatively thinmetallic layer .14 .on .a first side and a relatively thick paper layer15 on a second side. Intermediate these layers is a layer ofthermoplastic adhesive such as a heat sealable wax 16 having a thicknesscommensurate with the degree of sealing required when the sheet isemployed for its intended purposes. Along each of the side edges of theoverwrap, a band of laterally spaced rows of perforations is providedfor the purpose of directing the adhesive to the outer surface of themetallic layer during the sealing operation, these bands being showngenerally at 17 and 18 and comprising five such rows of perforations ineach band. As will later appear, the number of such rows of perforationsis not critical and may be more or less than the five rows as shownwithout departing from the invention. The overall dimensions of theoverwrap are, of course, chosen with respect to the article to beenwrapped, as, for example, the loaf of bread indicated by the dottedoutline 20 near the center of FIG. 6.

'Consideringnow FIG. 1, as conventional spooling machine may include-aframe portion 21 for rotatably supporting a driven shaft 22 to which isdetachably connected a take-up spool 23. A suitably controlled motor 24may drive shaft 22 by any conventional means such as a belt 25.Guiderolls 26, 27 may be mounted upon the spooler frame to direct theincoming perforated web toward the take-up spool after a generallyhorizontal passage from the supply roll 28. Similar guide rolls 29, 30may be mounted upon any suitable support to direct the imperforate webtoward the perforating apparatus.

The perforating apparatus may be mounted upon a stationary portion 31 ofthe spooler frame intermediate the pairs of guide rolls as be means ofspaced, fiat mounting plates 32 and 33 suitably affixed to the sides ofthe frame by bolts 34 (FIG. 1). As seen in FIG. 1, these mounting platesproject forwardly of the frame in the direction of the incoming web.Adjacent an upper projecting edge of the frame, inclined recesses 35 and36 are provided with an open end facing in the direction of the incomingweb and into which the stub shaft ends 37 and 38 of a backing roll 39are adapted to rest. This roll may include a cylindrical hollow tube ofmetal to which the stub shaft ends are aifixed. As an important featureof the invention, the metallic roll has a resilient covering 40 thereoninto which the final biasing energy of the perforating blades, later tobe described, is expended. As will be understood, the roll is driven bycontact of its covering with the paper layer of the travelling web. Ihave found that a covering of rubber having a durometer reading ofninety and a thickness of about inch is suitable for use with theperforating apparatus now to be described and when manufacturing anoverwrap as described in the example hereinafter disclosed.

As another feature of the invention, an adjustable shaft 41 serving thedual function of providing an initial positioning of the perforatingblades supported thereby and of forming a support with respect to whichthose blades may be carefully adjusted for variation of depth of webpenetration, is also provided.

This shaft extends parallel to roll 39 and may conveniently be mountedat one end in a pillow block 42 which may be adjustably clamped as bymeans of bolts 43 to a forwardly extending portion of plate 33 (FIG. 2).At its other end, the shaft is supported between complementary upper andlower bearing boxes 44 and 45. These bearing boxes may contain threadedholes for receiving bolts 46, 47 adjustably clamping the lower bearingbox to plate 32 and for receiving bolts 48, 49 for clamping the upperbearing box to the lower bearing box. At the end adjacent these bearingboxes, the shaft has rigidly affixed thereto a handle 50.

Depending upon the width of the web to be perforated, a number ofperforating assemblies, here shown as four, at 51, 52, 53 and 54, aremounted upon shaft 41 for support thereby. Considering now FIGS. 3 and4, each of the perforating assemblies includes a yoke member havingspaced arms 60 and 61 joined at a rear end by a cylindrical spacer 62having an aperture therethrough for reception of shaft 41 with a closebut freely movable fit. Suitably attached to the spacer as by welding,is a tangentially extending plate 63 projecting above and rearwardly ofshaft 41. A threaded aperture is provided in this plate adjacent itsrearmost end and engaging in the aperture is a selectively adjustablescrew 64 having an abutment 65 engaging at all times with a compressionspring 66.

Laterally disposed with respect to the yoke member is an L-shaped springbackboard member having a spring backing plate portion 67 and a shaftengaging portion 68. This latter port'on includes a generallysemi-circular recess, which recess fits against the under surface ofshaft 41, as best seen in FIG. 3. Cooperating with that latter portionis a cap member 69 adapted for clamping to the spring backboard memberas by bolts 70 and 71 on each side of shaft 41. Compression spring 66 ofcourse, bears at all times against the backing plate portion 67.

By means of the construction as thus far described, the shaft may beinitially set into prescribed angular relation with respect to themounting plates on the sides of the frame merely by rocking it withhandle 58 whereupon it may be locked into stationary position byadjustment of bolts 48 and 49 bringing the bearing boxes 44 and 45 intotight engagement with that shaft. If desired, a conventional rapidadjusting handle 59 may be employed for this purpose. Since the springbackboard members are securely clamped to the shaft by means of the capsbolted therewith, rocking movement of the shaft during this initialadjustment also rocks the spring backboard members. Moreover, due to thepresence of the compression springs the adjustment of the springbackboard members causes the yokes to pivot downwardly toward the web asseen in FIG. 1.

Carried between the arms of each yoke is one or more, preferablyidentical, perforating blades, five being shown in FIG. 4 at 74, 75, 76,77 and 78. These blades are mounted for rotation independently of eachother upon a pin 79 extending between the sides of the yoke and areprovided with a conventional friction reducing bearing, such as a ballbearing, permitting the blade to move easily. Since these blades servethe purpose of perforating the metallic layer of the overwrap to enableadhesive to be directed outwardly upon that metallic layer and are notfor the purpose of providing an overwrap weakening or tear-stripfunction, the construction, as well as the actuation of those blades issignificant. I have found that the length of the perforation formed bythe blade, as well as the spacings between adjacent perforations withinthe same row, is in general more important than the width betweenadjacent rows of perforations or the number of such rows ofperforations. Accordingly, I provide each of the perforating blades, onebeing shown at FIG. 5, with a series of peripheral sharp bevelled teethso, each of which is about & inch in length and which are spaced fromeach other bv an undercut 81 which likewise is about inch in length.

Accordin ly, it will be seen that the perforations in each row of thebands 17. and 18 (FIG. 6) are equal in length and are equally spacedwithin a given row, but that the perforations of one row are randomlyspaced as regards the perforations in an adjacent row due to theindependent rotation of the several perforating blades. The pattern ofperforations thus obtained may be designated as a sk p-score pattern inwhich the ends of adiacent perforations in a given row are separated bya brid e of metal helping to preserve the tensile strength of the web.

Having in mind the type of overwrap to be produced and theabove-described apparatus, mv method may be practiced as follows byreference to FIGS. 1 and 2. Operation of motor 24 rotates roll 23 at adesired speed wh ch imposes a tension on the web coming from supnlv roll28 and guided across backing roll 39 bv the several guide rolls.Frictional en agement of the paper side 15 of the web with the resilientcovering 40 of the backing roll causes that roll to rotate. By means ofap ropriate adjus ments. the shaft 41 occupies a position above themetallic surface of the moving web. which causes the vokes supported bthat shaft to hold the rotatable blades in enga ement with the metallicsurface of that web. The blades accordin ly are driven b their contactwith the web and cut into the thin metallic layer. The selected adin tnent of s rews 64 determi es the value of the biasin z spring pressurewhich is to be expended by the blade upon the web, the heavier suchpressure. the deeper the cut for a given web. and the lighter suchpressure the shallower the cut. Upon penetratin the metallic laver 14 (FG. 7) the blade encounters little or no resistance from the adhesive 16and if the spring biasing is sufficient to cause the blade to cut throuh the former. the blade extends its cut to the upper surface of thepaper layer as seen at 82. As will further be seen, the more the yokepivots about the shaft 41, the less will be the residual biasingpressure since the spring is diminishing its applied energy as itelongates. Therefore, when the blaoe touches the metallic layer, theentire web is pressed firmly against the covering of the backing rollwhich is sufficiently resilient to assist in reducing the tendency ofthe blade to bite too deeply into the web. The residual energy of thebiasing sprmg thus is opposed and absorbed by the rubber covered backingroll. Should the blade tips scratch the upper surface of the paperlayer, however, no appreciable weakening of the web occurs, since ingeneral the thickness of that paper layer is several times the thicknessof the metallic layer and, at the same time, the compression spring issubstantially fully extended by the time the blade tips reach the paperlayer. Thus, it will be seen that in carrying out the method, a gross orapproximate setting of the blades is first provided by the setting ofshaft 41, followed by a refine-:1 setting of the blade by application ofa spring biasing pressure, followed by expanding of any surplus biasingenergy upon the blade by absorbing that energy in the resilient backingroll. As the web moves through the perforating stage it is thusperforated in parallel bands the number of which depends upon the numberof perforating assemblies employed. If wrinkles or discontinuities arepresent in the incoming web, the separate perforating blades areunaffected since they rotate independently. No flaking or abrasion ofthe metallic layer occurs and no build-up of adhesive occurs on theblades since centrifugal force tends to keep the blades clean.

Overwrap made in accordance with the above process may be used forvarious purposes and for all such purposes possesses the self-sealingcharacteristic. As seen in FIG. 7, the several perforations 82 exposethe adhesive layer 16 so that when heat is applied to the metallic layer14, such adhesive may bleed outward upon that metallic surface. Also, asis well known in the art, the adhesive will bleed or strike-through thepores of the paper layer upon heat application. When enwrappinng a loafof bread for example, as seen in FIG.8, this bleeding is employed tofashion a longitudinal seam 19. In general, the

.most difficult seal and the one which heretofore has caused thegreatest problem, is the seal at the ends of that loaf. When the loaf isenwrapped by conventional wrapping apparatus which forms and tucks inthe wrapper, these tucks include metallic surfaces face-to-face andsince the loaf of bread is readily compressible, it is essentially thatthe overwrap be self-sealing upon application of a'heating means withrelatively little pressure. The present invention satisfies theserequirements since the band 17 of perforations permits ample adhesive tobleed through the perforations into an area near the ends of those tuckportions and to spread upon the metallic surfaces. Since aluminum is anexcellent conductor of heat, merely touching a heating means to thetucks near the ends of the loaf effects a rapid self-sealing which whenthe adhesive sets, will afford a substantially air-tight seal.

The tensile strength retainedby the overwrap following its perforatingis of significance as regards the enwrapping since many conventionalwrapping machines hold the overwrap which is furnished as a roll, undertension at one or more stages of operation. By reason of the presentinvention, the perforated self-sealing, overwrap may be used upon suchconventional machines since it does not tear along the perforated lines.

The advantageous features of the above described apparatus and method ofthe invention may be further seen by reference to the following specificexample of the particular overwrap article used for a standard size andshape of a loaf of bread.

Example The width of the overwrap was 15% inches and the length was 18%.inches. The outermost row of perforations of each bank was /8 inch fromthe side edge of the overwrap and the five rows were each 4 inch apart.Th perforations within each row were inch long and were spaced from eachother by 7 inch bridges of aluminum. The metallic layer comprised dryannealed aluminum foil, 0 temper and 0.00035 inch in thickness. Thepaper layer comprised fully bleached sulphite 20 pound bond paper havinga thicknes of about 0.002. inch (depending upon the density of thepaper). The wax layer comprised microcrystalline wax amounting to 16pounds of wax per ream of paper. A ream consists of 480 sheets 24 inchesby 36 inches. Following perforation, the described sheet retained atensile strength of 17.8 pounds per inch when subjected to stress in thedirection of the axis of the rows of perforations; of 3.54 pounds perinch when subjected to stress in a direction normal to the axis of thoserows; and of 7.65 pounds per inch when subjected to stress at 45diagonally of those rows. When sealed by lightly passing a heat sealingmeans into contact with the folded ends of the overwrap enclosing a loafof bread and after heat sealing the longitudinal seam 19, the overwrapprovided a substantially hermetic seal for the article enclosed thereby.During the enwrapping and sealing operation on high-speed packagingoperation no tearing of the overwrap along the rows ofperforationsoceurred.

In accordance with the patent statutes, I have described what at presentis considered to be the preferred embodiment of my invention, but itwill be obvious to those skilled in the art that various changes andmodifications may be made therein without departing from the true spiritand scope of the invention and I aim, therefore, to cover, in theappended claims, all such equivalent variations and modifications.

What I claim is:

1. In a laminated heat-scalable overwrap having a layer of metallic foilon a first side, a layer of paper on a second side, said paper layerbeing thicker than said metallic layer, and a layer of adhesiveintermediate said metallic and paper layers, the improvement comprising,two bands of perforations formed in said metallic layer for directingsaid layer of adhesive to the outer surface of said metallic layerduring the sealing thereof, said bands extending continuously along eachof two parallel side edges of said overwrap, each band comprising aplurality of laterally spaced rows of elongated perforations having eachperforation in each row spaced longitudinally of its adjacentperforation in the same row and extending in the same direction, eachband being of a size suflicient to provide within the confines of saidbands a substantial area of metal-to-metal contact upon folding of eachof said side edges upon itself, each perforation having a depthsufficient to fully penetrate said metallic layer and insufficient topenetrate said paper layer to a substantial weakening extent whilepenetrating at least part of said layer of adhesive, said overwrapcontaining said perforations having a greater tensile strength in theaxes of said bands of perforations than in the direction transverselythereof, the lateral spacing between adjacent rows of each band and thelongitudinal spacing between perforations within each row beingsufficiently great to overcome the tendency of said perforations to actas tear-strips during normal enwrapping and sealing operations employingsaid overwrap.

2. An overwrap as defined in claim 1 wherein the length of eachperforation within a row is substantially equal to the spacing betweenadiacent perforations in the same row.

3. An overwrap as defined in claim 1 wherein the perforations withineach row have a predetermined spacing rela* tive to each other and arandom spacing relative to the nearest perforation in adiacent rows.

4. An overwrap as defined in claim 1 wherein the length of eachperforation is about inch.

5. A product hermetically sealed by a laminated heatsealable overwrapcomprising: a product to be sealed; a heat-sealable overwrap envelopingsaid product; said heatsealable overwrap consisting of a layer ofmetallic foil on a first side, a layer of paper on a second side, alayer of adhesive intermediate said foil and paper layers, said layer offoil having two bands of elongated perforations extending continuouslyalong each of two parallel side edges of said erwrap, each bandcomprising a plurality of laterally spaced rows of perforations havingeach perforation in each row spaced longitudinally from its adjacentperforation in the same row; the perforations in each row being randomlyspaced relative to the perforations in adjacent rows, said laminatedoverwrap having each band of perforations folded about opposite ends ofsaid product to form at least some areas of foil to foil contact; andsaid foil to foil contact areas being sealed to each other by themigration of said layer of adhesive through the perforations in saidfoil layer upon the application of heat and pressure to the ends of saidproduct.

6. A product hermetically sealed by a laminated heatsealable overwrapcomprising: a product to be sealed; a heat-scalable overwrap envelopingsaid product; said heatsealable overwrap consisting of a layer ofmetallic foil on first side, a layer of paper on a second side, a layerof adhesive intermediate said foil and paper layers, said layer of foilhaving two bands of perforations extending continuously along each oftwo parallel side edges of said overwrap, each band comprising aplurality of laterally spaced rows of perforations having eachperforation in each row spaced longitudinally from its adjacentperforation in the same row; said laminated overwrap having eac band ofperforations folded about opposite ends of said product to form at leastsome areas of foil to coil contact and other areas of paper to foilcontact; said foil to foil contact areas being heat-sealed to each otherby the migration of said layer of adhesive through the perforations insaid foil layer and said areas of paper to foil contact being heatsealed by the migration of said layer of adhesive through the paperlayer to the foil layer.

7. A product hermetically sealed by a laminated heatsealable overwrapcomprising: a product to be sealed; a heat-sealable overwrap; saidheat-scalable overwrap consisting of a layer of metallic foil on a firstside, a layer of paper on a second side, a layer of adhesiveintermediate said foil and paper layers, said layer of foil having twobands of perforations extending continuously along each of two parallelside edges of said overwrap, each band comprising a plurality oflaterally spaced rows of perforations having each perforation in eachrow spaced longitudinally from its adjacent perforation in the same row;said laminated overwrap enveloping said product with its bands ofperforations being normal to the longitudinal axis of said product andwith its ends being overlapped forming a longitudinal seam parallel tothe longitudinal axis of said product; said longitudinal seam beingscaled by migration of said layer of adhesive through the paper layer tothe foil layer upon the application of heat and pressure to said seam;said laminated overwrap having each band of perforations folded aboutopposite ends of said product to form at least some areas of foil tofoil contact; and said foil to foil contact areas being sealed to eachother by the migration of said layer of adhesive through theperforations in said foil layer upon the application of heat andpressure to the ends of said product.

8. A production hermetically sealed by a laminated heat-sealableoverwrap comprising: a product to be sealed; a heat-scalable overwrapenveloping said product; said heat-sealable overwrap consisting of alayer of metallic foil on a first side, a layer of paper on a secondside, a layer of adhesive intermediate said foil and paper layers, saidlayer of foil having two bands of perforations extending continuouslyalong each of two parallel side edges of said overwrap, each bandcomprising a plurality of laterally spaced rows of perforations havingeach perforation in each row spaced longitudinally from its adjacentperforation in the same row; said laminated overwrap enveloping saidproduct with its hands of perforations being normal to the longitudinalaxis of said product and with its ends being overlaped forming alongitudinal seam parallel to the longitudinal axrs or said product;said longitudinal seam being sealed by migration of said layer ofadhesive through the paper layer to the foil layer upon the applicationof heat and pressure to said seam; said laminated overwrap having eachband of perforations folded about opposite ends of said product to format least some areas of foil to foil contact and other areas of paper tofoil contact, said foil to foil contact areas being heat-sealed to eachother by the migration of said layer of adhesive through theperforations in said foil layer and said areas of paper to foil contactbeing heat-sealed by the migration of said layer of adhesive through thepaper layer to the foil layer.

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